Too Small

I've been working on a lacy sort of jacket, this one to be precise, with the intent of wearing it over a dress I have to my older brother's wedding on May 13. I'm not nearly done with it, and it's hard to tell at this point, but I'm reasonably sure it's too small. 85% sure we'll say. Now my gauge measures almost exactly as it should - and yet it's too small! The same thing happened with the wool soakers (another of which I recently completed, by the way), my gauge was great but they just didn't turn out big enough. What the heck? I taught myself how to crochet so it's not surprising that I do it a little off. These projects are the first things I've done where gauge is important so I'm just now realizing how off I am and it's rather frustrating. Now I have to decide whether to start all over and use the same hook, just make the bigger sized jacket, or start all over with a bigger hook and make the same sized jacket. Either way I will be starting all over. Grrrr.